Conventionally, various projectors are suggested for various purposes. For example, it is suggested that an image projection portion is disposed in a mobile telephone and light emission from the projection portion is stopped when a change occurs in a predetermined region including a region onto which the light emitted from the projection portion is projected, and suggested that an acceleration sensor is disposed and a hand shaking correction is performed if a hand shaking vibration is detected (patent document 1). Besides, it is also suggested that in a hand-held projector, a vertex of a variable vertex prism is changed by an electromagnetic actuator based on a hand shaking detection signal from a sensor to prevent a projected image from being shaken by a hand (patent document 2).
Besides, as to hand shaking correction control, although not for a projector, but for a digital camera that incorporates an optical hand shaking correction function, it is suggested that in a case where a user intentionally performs a panning operation or a tilting operation, the hand shaking correction function is prohibited from working, and the hand shaking correction function is resumed by determining, with high accuracy, an end of a panning state or a tilting state (patent document 3). Further, as to a projector, it is suggested that a trapezoidal distortion correction of an image projected slantingly is performed by detecting a set angle of the projector (patent document 4). In the meantime, as to the trapezoidal distortion correction, it is also suggested that an upper side and a lower side of image data are exchanged with each other and the correction is performed by determining whether the projection screen is shifted from a wall surface to a ceiling or not, or shifted from a wall surface to a wall surface or not (patent document 5).